Plenty of other genetically engineered species in the galaxy. That, and along with the power of Genesis as a motivator, he'd have a lot of allies in no time at all.

Allies? Don't you mean mortal enemies?

The point they were trying to drive in TWOK, was that Kirk only managed to beat Khan via his experience and the efforts of his crew.

...And also that Khan had gone too crazy, and perhaps too old, to be the enemy he once was.

He did non of the above.

Hmh? Seems he did all of it.

He commandeered the ship, by cleverly making use of those slugs (and no doubt by other means, as the slugs would only get him so far in his quest to maroon the crew). After all, the ship was commandeered when we next met him.

He worked out how to use it. After all, he was using it when we next met him.

He then held his own against another starship in two battles. We saw that.

There's nothing extraordinary about what he did.

Now that's a completely different thing. It's standard fare for movie villains, but obviously none of us could have done anything of the sort in the time allotted, or even given a lifetime.

The first rule of seizure tactics it to fully secure the asset. It's been this way since pretty much the dawn of time. If Khan was really as smart as people claim he was, he would have know this and gone over EVERYTHING to find potential security leaks. the prefix codes would have stuck out like a swore thumb.

Bullshit. Of course the secret back door would be secret.

Come on, sensible people buy foreign combat vessels, aircraft and missiles in the real world. And they don't find all the back doors built into them, and not for lack of trying. But it's a risk they have to take, and it generally pays off.